Arrangement to protect capacitive loud-speakers against puncture



1929- M. VON ARDENNE 1,737,872

ARRANGEMENT TO PROTECT GAPACITIVE LOUD SPEAKERS AGAINST PUNCTURE Filed April 28, 1928 INVENTOR MANFRED VON ARDENNE RNEY both Patented Dec. 3,1929

UNITED I STATES MANFRE'D VON ARDENNE, OF BERLIN, GER-MAN ARRANGEMENT TO PROTECT CAPACITIVE LOUD-SPEAKERS AGAINST PUNCTURE Application filed April 28, 1928, Serial No. 273,633, and in Germany April 28, 1927.

The sensitiveness or responsiveness of a capacitive loudspeaker is so much greater, the smaller the distance between the two con ductive faces constituting a condenser, one 5 of which or both form the diaphragm or diaphragms, as the case may be, of the loudspeaker. On the other hand, in order to produce great sound-pressure amplitudes with a capacitive loudspeaker, it is necessary that coats should be capable of having very considerable A. C. or D. C. pd.s impressed thereon. However, on account of the small distance to be chosen for the two coats of the capacitive loudspeaker for the reasons hereinbefore set forth, there arises the danger of the high pd.s between the condenser coats being equalized across the intervening medium or the insulating parts between them, in other words, of a breakdown being caused in the capacitive loudspeaker. Since such a breakdown is liable to result in an arc between the condenser coats of the loudspeaker, when they are connected with a source of current which serves for the production of a input side, said inputcomprising an o mic pd., and since the arc may thus be maintained from the source of current, there arises the risk of the loudspeaker being totally disabled as a consequence of such a breakdown.

Now, the present invention discloses ways and means whereby the said inconvenience and danger in the use of capacitive loudspeakers is to be obviated, such protective means being adapted to prevent the establishment of an arc in case of puncture.

The accompanying drawing shows schematically one embodiment of my invention. This protection device consists of a highohm resistance 1, inserted in one of the supply leads connected with one of the condenser coats of the loudspeaker 2, said resistance being shunted by a condenser 3 of high capacity. The resistance value of the said high-ohm resistance should be as high as possible, though low compared with the insulation resistance of the loudspeaker. In this way, it does not impair the feed of the D. C. voltage required for the operation of the loudspeaker, though it prevents the production of a strong D. G. which would be required for arcing in case of a breakdown,

at any rate, it diminishes or limits the D. C.

pd. across-the condenser coats of the loudspeaker in case of the striking of an arc to such an extent that the arc will go out at once. The condenser connected in parallel to the high-ohm resistance must possess ads-- quately high capacity in order that the A. C.

required for the "operation of the loudspeaker may be fed through the same. Hence, the capacity of the condenser must be several times higher than the capacity of the loudspeaker,

while, on the other hand, it should not be so'high that a discharge of the condenser through the loudspeaker is liable to damage the latter.

Having thus described my invention, what I desire to protect by Letters Patent is as follows:

1. Means for protecting capacitive loudspeakers against breakdown, comprising a high ohmic resistance and a condenser shunted across said resistance in an inputlead of said loudspeaker.

2. A capacitive loudspeaker havin an resistance and a condenser in parallel therew1th,-sa1d ohmic reslstance havlng a value comparatively small to the insulation resistance of said loudspeaker.

3. In capacitive loudspeakers, means for protecting the loudspeaker against breakdown, comprising a high-ohm resistance arranged in series with a conductor leading to one of the diaphragm electrodes of the loud.- speaker, and a capacity in said conductor and in parallel with the resistance, the value of the said high-ohm resistance being the insulation resistance of the loudspeaker, and the value of-the said capacity being greater than the capacity of the loudspeaker.

4. In capacitive loudspeakers, means for protecting the loudspeaker against breakdown, comprising a high-ohmic resistance in series with a conductor leading to a diaphragm electrode of the loudspeaker and a condenser in said conductor and arranged in parallel with said resistance.

BARON MANFRED VON ARDENNE. 

